Generally, in silver halide photographic materials, for the purpose of adjusting sensitivity, improving safelight aptitude, adjusting color temperature of light, preventing halation, or adjusting balance of sensitivity in multi-layer color photographic materials, it is conventionally practiced that a light-absorbing compound is contained in a silver halide emulsion layer or other hydrophilic colloid layer, so that light having a specific wavelength may be absorbed.
For example, silver halide photographic materials have a support on which hydrophilic colloid layers, including a photosensitive silver halide emulsion layer, are formed, and when said photosensitive silver halide emulsion layer is exposed to light image-wise to record an image, it is required to control the spectral energy distribution of the entering ray into the said silver halide emulsion layer in order to improve photosensitive sensitivity. In this case, usually, a technique is taken wherein only light in the intended wavelength range is allowed to transmit, by incorporating a dye capable of absorbing light in the wavelength range undesired for said photographic silver halide emulsion layer into a hydrophilic colloid layer located farther away from the support than the said photographic silver halide emulsion layer, thereby allowing the hydrophilic colloid layer to act as a filter layer.
As for antihalation layers, for the purpose of improving sharpness of an image, an antihalation layer is provided between a photosensitive emulsion layer and a support or to the back of a support, so that detrimental reflected light at the interface between the emulsion layer and the support or at the back of the support is absorbed, thereby improving sharpness of the image.
Further, for the purpose of increasing sharpness of an image, a dye capable of absorbing light in the wavelength range in which a silver halide is photosensitive is used in a silver halide emulsion layer, to prevent irradiation.
Particularly, in silver halide photographic materials used in photomechanical processes, more particularly in photographic materials for daylight rooms, a dye for absorbing UV rays or visible light is added to photosensitive layers or to a layer located between a light source and photosensitive layers, in order to increase safety against light from a safelight.
In X-ray photographic materials, in some cases, a colored layer for improving sharpness is provided so as to act as a crossover cut filter for decreasing crossover light.
In many cases, these layers to be colored are made up of a hydrophilic colloid, and therefore generally for the coloring a dye is contained in the layer. The dye is required to meet, for example, the following conditions.
(1) The dye has spectral absorption appropriate to the intended purpose.
(2) The dye is photographically inactive. That is, the dye does not detrimentally affect chemically the performance of silver halide emulsion layers, for example it does not lower sensitivity or cause latent image fading or fogging.
(3) The dye can be decolored or dissolved and removed in photographic processing steps, so that no detrimental color will remain on the photographic material after the processing.
(4) The dye is excellent in stability after a lapse of time and keeps the quality in the coating liquid (solution) or the silver halide photographic material.
Efforts have been made to find dyes that meet these conditions. For example, pyrazoloneoxonol dyes described in British Patent No. 506,385, barbituric acid oxonol dyes described in U.S. Pat. No. 3,247,127, azo dyes described in U.S. Pat. No. 2,390,707, styryl dyes described in U.S. Pat. No. 2,255,077, hemioxonol dyes described in British Patent No. 584,609, merocyanine dyes described in U.S. Pat. No. 2,493.747,, cyanine dyes described in U.S. Pat. No. 2,843,486, and methylenetype benzylidene dyes described in U.S. Pat. No. 4,420,555 can be mentioned.
To secure that the layer containing the above dye serves as a filter layer or an antihalation layer, it is required that the particular layer be selectively colored, and substantially the coloring should not affect other layers. This is because if the other layer is substantially colored, not only the other layer is spectrally affected detrimentally but also the effect of the filter layer or the antihalation layer is reduced. If the dye added to a particular layer to prevent irradiation diffuses and colors other layers, a problem similar to the above will occur.
To solve this problem, conventionally a means is known wherein a so-called acid dye having a sulfo group or a carboxyl group is localized in a specific layer using a mordant.
Such a mordant includes, for example, ethylenically unsaturated compound polymers having dialkylaminoalkyl ester residues, described in British Patent No. 685,475, reaction products of polyvinyl alkylketones with a aminoguanidine described in British Patent No. 850,281, and vinylpyridinium cationic polymer and vinylpyridine polymers described in U.S. Pat. Nos. 2,548,564, 2,484,430, 3,148,061, and 3,756,814 and to make the above-mentioned acid dye effectively mordanted, cationic mordants containing secondary and tertiary amino groups, nitrogen-containing heterocyclic groups, and their quatenary cationic groups in the polymers are used.
However, if a mordant is used, when the layer to which the dye is added comes in contact with other hydrophilic layer in a wet state, diffusion of part of the dye from the former layer to the latter layer often occurs in some cases. Such diffusion of a dye depends on the chemical structure of the mordant as well as on the chemical structure of the dye used.
Further, if a polymer mordant is used, after photographic processing, in particular after photographic processing whose processing time is shortened, colored residue is particularly liable to remain on the photographic material. It is considered that although the bonding strength of the mordant to the dye becomes considerably weak in an alkaline solution, such as a developer, some bonding strength still remains and therefore the dye or reversibly decolored products remain in the layer containing the mordant.
However, these cationic mordants statically interact with gelatin often used as a hydrophilic colloid and a surface-active agent having an alcoholate group, a carboxylate group, a sulfonate group, or a sulfate group, which agent is used commonly as a coating auxiliary, leading to deterioration of coating properties in some cases.
In some cases of color photographic materials, desilvering properties are deteriorated and the sensitivity of the adjacent emulsion layers is lowered.
It is frequently noticed that the above-mentioned acid dye used together with such a mordant diffuses into another layer, and therefore it is considered to use a large amount of a mordant to obviate the diffusion, but not only can the diffusion not be obviated completely, also the thickness of the layer in which the acid dye is contained increases, which disadvantageously causes the sharpness to lower.
In photographic materials for printing reproduction, generally a reducing operation using a reducing solution for adjusting the concentration, the gradation, etc., is performed, and since the reducing solution contains a water-soluble iron complex as a reducer, when the above-mentioned cationic mordant is used, the cationic mordant bonds statically to the iron complex, thereby disadvantageously causing yellow stain due to the iron complex.
These disadvantages can be improved by the use of a dye described in JP-A ("JP-A" means unexamined published Japanese patent application) No. 280246/1988, but there is a defect that the decoloring property is unsatisfactory, particularly in low-pH rapid processing.
In the case of color photographic materials, for the purpose of absorbing yellow light and of preventing halation, colloidal silver is conventionally used. This colloidal silver causes, however, a problem that the photosensitive silver halide emulsion layer adjacent to the colloidal silver layer increases in fogging, which is desired to be solved.
As other means of retaining a dye in a particular layer of a photographic material, techniques are known as described in JP-A Nos. 12639/1981, 155350/1980, 155351/1980, 92716/1977, 197943/1988, 27838/1988, and 40827/1989, European Patent Nos. 0015601 B 1 and 0276566 A 1, and International Patent Application Publication No. 88/04794, in all of these a dye is permitted to present in a dispersed solid form.
However, when a dye is made to be in a dispersed solid form, as is described in the above-mentioned International Patent Application Publication No. 88/04794, it is apparent that the absorption peak of the absorption spectrum of the covering of the dispersed solid shifts in comparison with the absorption spectrum of the solution of the same dye or with the absorption spectrum of the dye dissociated at a pH of 10, so that the half band width (HBW) is characteristically broadened.
If the half band width is broadened, some cases are suitable for application to filters, wherein exposure to light in a wide wavelength range is required, but there is a defect that the value of the absorbance decreases generally. Further, in multilayer silver halide photographic materials, the too broad half band width is disadvantageous, on the contrary, in the application to filters, such as yellow filters and magenta filters, wherein light having undesired wavelengths in the spectral sensitivity region at a lower layer are to be cut, and when a dispersed solid dye is used as a safelight filter layer, as described in JP-A No. 110453/1990. Further, when a dispersed solid dye is used in an antihalation layer of a sensitive layer whose spectral sensitive region is present in a very narrow wavelength region, or is used in an antihalation layer of a case that will be exposed to light in a very narrow wavelength region, that the absorbance is low requires a large amount of a dye for coating, resulting in many disadvantages, for example that decoloring properties are deteriorated, that the thickness of the film is increased, and that the cost increases.